Tải bản đầy đủ - 0 (trang)
8 Other Targets for Molecular Identification of Insects

8 Other Targets for Molecular Identification of Insects

Tải bản đầy đủ - 0trang

5



Molecular Identification of Mealybugs



phosphogluco isomerase 25. phosphoenol

pyruate carboxy kinase 26. prune 27. copper,

zinc superoxide dismutase 28. sodium channel

para locus I 29. snail 30. timeless 31. triosephosphate isomerase 32. vestigial 33. white

34. wingless 35. xanthine dehydrogenase 36.

yolk protein 1 and 2 37. zeste.



5.9



Limitations



• May be heterozygous and present in low copy

numbers.

• Many genes contain large introns that makes it

difficult to amplify more than one exon.

• Many single-copy loci are actually are present

in more than one copy.

• Pseudogenes may create problem if comparisons are made inadvertently.

Even with all the limitations, the molecular

identification of insects employing mtCOI is

gaining momentum, and as of now it can be an

effective adjunct tool for the integrated taxonomy. Many barcoding initiatives are beginning to

take shape, such as the recent initiative on

Barcoding of butterflies of India funded by the

Department of Biotechnology. With the increase

in international trade on agricultural produces

where the danger of introduction of invasive species looms large, DNA barcoding is going to play

a vital role in the quick identification of insectpests at the port of entry. As ambitiously envisaged, the development and deployment of the

hand-held sequencer, which is supported by the

global networked database, is going to revolutionize the way we identify insects that are

already described, along with the new ones.



5.10



Applications



1. The relationship of six mealybug species (Pl.

citri, Pl.ficus, P.ovae, Ps.longispinus, Ps.vibruni,

Ph.aceris) was studied using randomly amplified

polymorphic DNA-polymerase chain reaction

(RAPD-PCR) in Turkey. Cluster analyses of



85



RAPD data clearly separated the species into

two groups (Serce et al. 2007).

2. Seven species of mealybugs (Ps maritimus,

Ps.vibruni. Ps.longispinus, Ps.calceolariae,

Pl.ficus, Pl.citri, Ferrisia gilli Gullan) were

identified using a Multiplex PCR based on the

mitochondrial cytochrome oxidase subunit

gene (Daane et al. 2011).

3. There was a slight difference in morphological characters in the populations of

Planococcus ficus, indicating that there are

two different populations of the same species

in Tunisian vineyards. Likewise, in the molecular analyses, two separate clades were

revealed in the neighbour-joining phylogenetic tree, supporting the morphological studies and suggesting there are two distinct

populations of grape vine in Tunisia, which

might be two different biotypes (Mansour

et al. 2012).



References

Andersson SG, Kurland CG (1998) Reductive evolution

of resident genomes. Trends Microbiol 6:263–268

Asokan R, Rebijith KB, Singh SK, Sidhu AS, Siddharthan

S, Karanth PK, Ellango R, Ramamurthy VV (2011)

Molecular identification and phylogeny of Bactrocera

Species (Diptera: Tephritidae). Fla Entomol

94:1026–1035

Brunner PC, Chatzivassilious EK, Katis NI, Frey JE

(2004) Host associated genetic differentiation in

Thrips tabaci (Insecta: Thysanoptera), as determined

from mtDNA sequence data. Heredity 93:364–370

Caterino MS, Cho S, Sperling FAH (2000) The current

state of insect molecular systematics: a thriving tower

of Babel. Ann Rev Entomol 45:1–54

Daane KM, Middleton MC, Sforza R, Cooper ML, Walton

VA, Walsh DB, Zaviezo T, Almeida PP (2011)

Development of a multiplex PCR for identification of

vineyard

mealybugs.

Mol

Ecol

Evol

40(6):1595–1603

Downie DA, Gullan PJ (2004) Phylogenetic analysis of

mealybugs (Hemiptera: Coccoidea: Pseudococcidae)

based on DNA sequences from three nuclear genes,

and a review of the higher classification. Syst Entomol

29:238–259

Folmer O, Black M, Hoe W, Lutz R, Vrijenhoek R (1994)

DNA primers for amplification of mitochondrial cytochrome c oxidase I from diverse metazoan invertebrates. Mol Mar Biol Biotechnol 3:294–299



86

Foottit RG, Maw HEL, Pike KS, Miller RH (2010) The

identity of Pentalonia nigronervosa and P. caladii van

der Goot (Hemiptera: Aphididae) based on molecular

and morphometric analysis. Zootaxa 2358:25–38

Hajibabaei M, Janzen DH, Burns JM, Hallwachs W,

Hebert PDN (2006) DNA barcodes distinguish species

of tropical Lepidoptera. Proc Natl Acad Sci U S A

103:968–971

Hall TA (1999) BioEdit: a user-friendly biological sequence

alignment editor and analysis program for Windows

95/98/NT. Nucleic Acids Symp Ser 41:95–98

Hebert PDN, Gregory TR (2005) The promise of DNA

barcoding for taxonomy. Syst Biol 54:852–859

Hebert PDW, Cywinska A, Ball SL, deWaard JR (2003a)

Biological identification through DNA barcodes. Proc

Roy Soc Lond B 270:313–321

Hebert PDN, Cywinska A, Ball SL, DeWaard JR (2003b)

Biological identifications through DNA barcodes.

Proc Roy Soc B Biol Sci 270:313–322

Hebert PDN, Ratnasignham S, deWaard JR (2003c)

Barcoding animal life: cytochrome c oxidase subunit 1

divergences among closely related species. Proc Roy

Soc Lond Ser B 270(Suppl. 1):S96–S99

Mansour R, Cavalleri V, Mazzeo G, Lebdi KG, Russo A

(2012) A morphological and molecular characterization of vine populations (Hemiptera, Pseudococcidae)

from Tunisia. J Entomol Acarol Res 44(e5):24–27

Mayr E, Ashlock PD (1991) Principles of systematic zoology, 2nd edn. McGraw-Hill, New York

Meyer JB, Kasdorf GGF, Nel LH, Pietersen G (2008)

Transmission of activated-episomal banana streak ol

(badna) virus (bsolv) to cv. Williams banana (musa sp.)

by three mealybug species. Plant Dis 92:1158–1163

Millar IM (2002) Mealybug genera (Hemiptera:

Pseudococcidae) of South Africa: identification and

review. Afr Entomol 10:185–233

Miller DR, Miller GL, Watson GW (2002) Invasive species of mealybugs (Hemiptera: Pseudococcidae) and

their threat to US agriculture. Proc Entomol Soc Wash

104:825–836

Miller DR, Miller GL, Hodges GS, Davidson JA (2005)

Introduced scale insects (Hemiptera: Coccoidea) of

the United States and their impact on us agriculture.

Proc Entomol Soc Wash 107:123–158

Min XJ, Hickey DA (2007) DNA barcodes provide a

quick preview of mitochondrial genome composition.

PLoS ONE 2(3), e325

Moran NA, McCutcheon JP, Nakabachi A (2008)

Genomics and evolution of heritable bacterial symbionts. Ann Rev Genet 42:165–190

Mullis KB, Faloona FA (1987) Specific synthesis of DNA

in vitro via a polymerase-catalyzed chain reaction.

Methods Enzymol 155:335–350

Nakaune R, Toda S, Mochizuki M, Nakano M (2008)

Identification and characterization of a new vitivirus

from grapevine. Arch Virol 153:1827–1832



K.B. Rebijith et al.

Park DS, Suh SJ, Oh HW, Heber PDN (2010) Recovery of

the mitochondrial COI barcode region in diverse

Hexapoda through tRNA-based primers. BMC

Genomics 11:423

Park DS, Suh SJ, Hebert PDN, Oh HW, Hong KJ (2011)

DNA barcodes for two scale insect families, mealybugs (Hemiptera: Pseudococcidea) and armored scales

(Hemiptera: Diaspididae). Bull Entomol Res

101:429–434

Rebijith KB, Asokan R, Krishna Kumar NK, Srikumar

KK, Ramamurthy VV, Shivarama Bhat P (2012) DNA

barcoding and development of species-specific markers for the identification of Tea mosquito bugs

(Miridae: Heteroptera) in India. Environ Entomol

41:1239–1245

Rubinoff D (2006) Utility of mitochondrial DNA barcodes in species conservation. Conserv Biol

20:1026–1033

Rubinoff D, Cameron S, Will K (2006) A genomic

perspective on the shortcomings of mitochondrial

DNA for “Barcoding” identification. J Hered 97:

581–594

Saccaggi DC (2006) Development of molecular techniques to identify mealybugs (Hemiptera:

Pseudococcidae) of importance on grapevine in South

Africa. University of Pretoria, Pretoria

Sambrook J, Russell M (2001) Molecular cloning: a laboratory manual, 3rd edn. Cold Spring Harbor Laboratory

Press, New York

Sambrook J, Fritsch EF, Maniatis T (1989) Molecular

cloning: a laboratory manual, 2nd edn. Cold Spring

Harbor Laboratory Press, New York, 1659p

Serce CU, Kaydan MB, Kilincer AN, Ertunce F (2007)

Investigation of mealybug (Hemiptera: Coccoidea:

Pseudicoccidae)

species

from

Turkey

by

RAPD. Phytoparasitica 35(3):232–238

Shufran KA, Burd JD, Anstead JA, Lushai G (2000)

Mitochondrial DNA sequencedivergence among

greenbug (Homoptera: Aphididae) biotypes: evidence

for hostadapted races. Insect Mol Biol 9:179–184

Smith MA, Woodley NE, Janzen DH, Hallwachs W,

Hebert PDN (2006) DNA barcodes reveal cryptic

host-specificity within the presumed polyphagous

members of a genus of parasitoid flies (Diptera:

Tachinidae). Proc Natl Acad Sci U S A

103:3657–3662

Stoeckle MY, Zemlak TS, Francis CM (2004)

Identification of birds through DNA barcodes. PLoS

Biol 2(10), e312

Sunnucks P, Hales DF (1996) Numerous transposed

sequences of mitochondrial cytochrome oxidase I-II in

aphids of the genus Sitobion (Hemiptera: Aphididae).

Mol Biol Evol 13:510–524

Zhang DX, Hewitt GD (1996) Nuclear integrations: challenges for mitochondrial DNA markers. Tree

11:247–251



6



Biology

M. Mani and C. Shivaraju



A few generalizations on the biology of mealybugs are derived primarily from the detailed studies of the work previously done on common

mealybug species. There are slight variations in

the biology of mealybugs among the species.



6.1



Reproduction



The mature or gravid adult female begins to grow in

size as the ovaries develop, ending at about 4–5 mm

in length and far less dorso-ventrally flattened. The

adult male is about 1.5 mm in length, with long

wings, a brown-coloured body and two multi-segmented antennae that are about half the length of

the body. Mealybugs have the lecanoid type of the

paternal genome elimination system, where both

sexes develop from fertilized eggs (i.e., diploidy),

but during the early stage of development of the

male, the paternal half is deactivated through heterochromatinization. This system suggests that the

females would produce a male-biased sex ratio

when alone and a more female-biased sex ratio

when grouped with other females. Mealybug reproduction can be quite variable. For some mealybugs,

mating is probably necessary, although facultative

parthenogenesis has been reported for Planococcus

M. Mani (*) • C. Shivaraju

Indian Institute of Horticultural Research,

Bangalore 560089, India

e-mail: mmani1949@yahoo.co.in



citri (Risso). To attract adult males, the females

emit a sex pheromone. Female mealybugs mate

multiple times and the number of times they mate

also affects the egg production. Parthenogenetic

reproduction is also observed in many mealybug

species, while in some others, reproduction is by

both sexual and parthenogenetic means.

Most mealybug species reproduce sexually, as

well as lay eggs. However, some species such as

Phenacoccus solani Ferris, Phenacoccus parvus

Morrison and Ferrisia malvastra (McDaniel)

reproduce parthenogenically and others, for example, Pseudococcus longispinus (Targioni Tozzetti)

and Antonina graminis (Maskell) are ovoviviparous. Two different genetic systems may be found

in mealybugs; the more common corresponds to a

particular type of haplodiploidy known as paternal

genome elimination in which both males and

females develop from fertilized eggs. The male

develops from a zygote containing one haploid

genome from his mother and one haploid genome

from his father, but only the maternal genome is

transmitted to the offspring via the sperm, because

the set of chromosomes of paternal origin becomes

heterochromatic and genetically inactive. Male

mealybugs are thus functionally haploid, owing to

heterochromatization (parahaploidy). The other

genetic system is thelytokous parthenogenesis, in

which there are no males and therefore no mating

occurs. There are no sex chromosomes in mealybugs; sex is probably determined by a functional

haploidy/diploidy mechanism, which seems to be



© Springer India 2016

M. Mani, C. Shivaraju (eds.), Mealybugs and their Management in Agricultural

and Horticultural crops, DOI 10.1007/978-81-322-2677-2_6



87



M. Mani and C. Shivaraju



88



dependent on the behaviour of a set of chromosomes and not on a single chromosome. If heterochromatization of an entire set of chromosomes

takes place during the cleavage stage of embryogenesis, the embryo will develop into a male, or

otherwise into a female. Spermatogenesis is characterized by inverse meiosis and the absence of

chromosome pairing and genetic recombination

where the genome of the mother determines the

heterochromatization of the inherited paternal

chromosomes in mealybug embryos. According

to this model, heterochromatization is controlled

by a maternal factor, with the maternally derived

chromosomes imprinted so that they do not suffer

the fate of the male chromosome. Sex determination in mealybugs, and consequently the sex ratio,

is known to be influenced by temperature and the

age of the mother. The effect of the temperature or

the age of the mother on the sex ratio of the offspring is attributed to a change in the ratio between

the numbers of oocytes with and without the

maternal factor.



The male is holometabolic and develops

through four stages, egg, larva (two nymphal

instars), pupa and adult, while the female is

hemimetabolic and develops through three

stages, egg, larva (three nymphal instars) and

adult.



6.1.1



Oviposition



Mealybugs may be oviparous, viviparous or ovoviparous. Although variable, the pre-oviposition

period is 4–5 days in general. In most of the

mealybugs like Pseudococcus longispinus,

Ferrisia gilli Gullan, Dysmicoccus brevipes

(Cockerell) and Heliococcus bohemicus Sulc.,

eggs are laid by the adult female among the filamentous secretion of the ovisac formed by the

pores on the adult's body. Wax secreted by the

numerous pores and ducts around the ovipositional opening plays an important role in

forming a waxy sac around the laid eggs. The



6 Biology



ovisacs are somewhat variable in their structure,

depending upon the species of the mealybug.

Several types of ovisacs have been recorded,

varying from one covering the entire female

body, to one covering only half or perhaps the

last two abdominal segments, to one which is

entirely ventral. These ovisacs are normally

deposited on the shoots, fruits, flowers, leaves,

underneath the bark and the cracks and crevices

of the plant stem and arms.

The eggs are oval and can be seen with the

naked eye, while the colour of the eggs varies

with the species. The normal oviposition period

of female mealybugs is 6–8 days, but it differs

depending upon the species and climatic conditions. They are in close proximity in the ovisac.

Female mealybugs are capable of mating multiple times on the same day and the female reproductive output is unaffected by multiple

copulations. As many as 600 eggs can be laid by

one female, but the number of eggs varies according to the mealybug and the host species. Freshly

laid eggs vary in colour in different species, for

example, the eggs are orange in case of

Maconellicoccus hirsutus (Green), violet in case

of Nipaecoccus viridis (Newstead), yellow in

case of most of the mealybugs like Planococcus

citri (Risso). However, the colour changes

slightly before hatching, and the size also varies

in different species. In the case of M. hirsutus, the

eggs are 0.34–0.38 mm in length and the width

ranges from 0.17 to 0.20 mm. Most of the mealybugs are oviparous and they lay eggs in the ovisac. But some mealybugs are ovoviviparous

(depositing live first instars); for example,

Dysmicoccus brevipes (Cockerell) bears live

young, producing as many as 908 crawlers. These

ovoviviparous females produce little or no ovisac

and apparently shield their young for a short time

by covering them with their abdomen. This character is particularly true of Puto, a genus which,

for the most part, is ovoviviparous. Planococcus

lilacinus (Cockerell) also lays the crawlers

directly, while Ferrisia virgata (Cockerell) lays

eggs which hatch immediately after laying. The

number of offspring produced per female varies



89



depending on the species, environmental conditions and food supply. It has been reported ranging from about 50 to over 800. In the absence of

adult males, the virgin females of Planococcus

minor (Maskell) do not produce eggs.



6.1.2



Incubation



The eggs hatch between 4 and 10 days, depending on the temperature and humidity. Hatching

percentage ranges from 80 to 90 %.



6.1.3



Nymph



Mealybugs generally have three larval instars for

females and four for males. Each of these stages

resembles the previous one, except for an increase

in size and the amount of wax secreted. Usually,

immature males are slightly longer and more

slender than females.



6.1.4



First-Instar Nymph (Both

Sexes)



The eggs hatch into first-instar nymphs or crawlers and are vulnerable to insecticidal applications. This stage usually has proportionally very

large legs and antennae compared with other

instars and often there are fewer antennal segments than in the adult. This crawler is often

quite mobile and usually migrates to other hosts,

or at least to diverse areas of the parent host.

There is no reliable character to distinguish

between the male and female at this stage. The

mean duration of the first instar is about 6–7

days; there is not much variation between male

and female instars, but it can vary under different

conditions of temperature and humidity. When

viewed from above, it seems elongate oval in

shape, but is extremely flat from the side. The

first-instar nymph is often free from the waxy

coating which usually develops at the later stages

of growth.



M. Mani and C. Shivaraju



90



6.1.5



Second-Instar Nymph (Both

Sexes)



The second-instar nymph emerges through a slit

in the medio-dorsum of the head and thorax of

the first-instar skin. The legs and antennae are

still proportionally larger compared to the adult

body and often there are fewer antennal segments

than in the adult. During this stage, it is possible

to differentiate between the sexes, for by the end

of this instar, the males produce a filamentous sac

or cocoon over their bodies. The rostrum of the

male is lost after the first moult, making the recognition of the second-instar male quite simple.

The second nymphal stage of the female is characterized by the presence of six jointed antennae,

four pairs of cerarii in the abdominal segments

VI–IX and the oral rim ducts are restricted to the

dorsum. In the second stage, the male only has

one pair of, rarely two pairs of, cerarii and tubular

ducts of oral collar type both on the dorsum and

the venter. Mean duration of the second instar is

about 6–7 days, but not much variation is seen

between male and female instars, though it can

be variable under different conditions of temperature and humidity.



6.1.6



Third-Instar Nymph (Both

Sexes)



The second-instar skin is shed in the same manner as the first, producing the third-instar nymph.

In female specimens, these instars begin to take

the normal shape of the adult. Legs and antennae

are approximately in proportion to the body size,

when compared with the adult and the antennal

segments are normally, but not always, the same

in number as in the mature forms. The duration of

the third instar in females is usually about 8 days,

but it can vary under different conditions of temperature and humidity. In the male, the second

skin is shoved to the posterior portion of the

cocoon; the third-instar male is called the prepupa and is usually much smaller and more elongated than the third instar female. It also differs

because it has wing pads, no rostellum and more

antennal segments. The duration of the third-



instar male is about 1 day, but it again varies

according to temperature and humidity conditions for different species.



6.1.7



Fourth-Instar Male



The fourth instar of the male is produced in a

cocoon and is known as the pupa. The third skin

that is shed is again shoved to the back of the

cocoon. This instar differs from the previously

mentioned one; it has two longer, backwardly

directed wing pads, more antennal segments (tenjointed, normally the same as the adult) with a

few pointed setae and three pairs of eyes. At one

point between this instar and the next, a break in

the posterior part of the cocoon is formed and the

fourth shed skin is pushed outside. The duration

of the fourth instar/pupa is about 6 days, but it

again varies under different conditions of temperature and humidity.



6.1.8



Adult Female



The adult female is almost similar to the thirdinstar female nymph. The third-instar female has

seven-jointed antennae and five pairs of cerarii in

the abdominal segments V–IX, but the adult

female has nine-jointed antennae, six pairs of

cerarii in the abdominal segments IV–IX., valvular opening and multilocular disc pores in the

venter. The fourth-instar female emerges in the

usual manner to become an adult. The female

nymph can be distinguished from all of the

nymphal instars by the presence of a vulva and it

is often very large and distorted from the eggs or

nymphs which she carries in her abdomen. The

female nymph has various types of pores on its

body; the circular multilocular and pentagonal

quinquelocular pores are believed to function in

the production of the filamentous ovisac, whereas

the normally more abundant trilocular pores

function in the production of the white powdery

secretion, characteristic of mealybugs. The exact

function of any of these pores has yet to be confirmed and the precise morphological structure of

the various types of tubular ducts is still unknown.



6 Biology



In certain mealybug species, such as Ferrisia virgata, it is believed that the enlarged tubular ducts

produce thin crystalline rods, but the importance

of the smaller tubular duct remains a mystery.

The setae of the cerarii are apparently important in supporting the filaments; again, in most

adult female mealybugs, two pairs of dorsal cavities or ‘ostioles’, as they are called, can be located

submarginally. The posterior pair is on the seventh

abdominal segment and the anterior pair is apparently on the head. As previously mentioned, the

ostioles, when irritated, seem to function in the

secretion of globules of body fluid, perhaps as a

defensive mechanism. It is also believed that these

dorsal openings function in the exit of honeydew

for consumption by ants. The filaments which may

be seen so often on the lateral margins of many

mealybugs are apparently produced by the clusters

of trilocular pores surrounding the cerarii.

Other structures of the adult female are the

antennae, the eyes, mouthparts, legs, spiracles,

vulva, circulus, anal ring, anal lobes, body setae

and cerarii. The antennae of mealybugs are filiform, with the terminal segments characteristically longer and wider than the preceding ones.

There is a slight noticeable tapering of the antennae from the first segment to the last and the

antennal segmentation varies in number from two

in some species of Antonina to nine in certain

species of Phenacoccus. Antennal shape is

important in the field identification of some subterranean mealybugs. The unusually short geniculate antennae of Rhizoecus, Pygmaeococcus and

Geococcus are easily recognized, particularly

when compared with the normal, straight antennae of most other genera, which makes their field

identification quite simple. There are often some

enlarged setae on the apical, two antennal segments, which apparently act as special sensory

setae. These setae differ from the other antennal

setae, being larger in diameter and more rounded

at the tip. The eyes of mealybugs are compound

and they function only in distinguishing between

light and dark.

The legs of mealybugs have a characteristic

colour. For example, the legs of Rhizoecus and

Misericoccus are white, those of many species of

Phenacoccus and Spilococcus are red, while



91



these of Pula are very dark brown or almost black

in colour. Leg size is also quite variable:

Antoninoides have very small, reduced legs;

Discococcus have slightly larger legs;

Phenacoccus, Spilococcus, Chorizococcus and

others bear proportionately normal sized legs;

and the numerous Puto species bear very enlarged

and robust legs. The adult females of Antonina

are totally without legs (apodous); on each surface of the posterior part of the trochanter, there

are normally two, sometimes three, small clear

spots which are sensory in function. On the tarsal

segments and on the claw, mealybugs normally

have a pair of spatulate setae, but these are sometimes absent. The use of these setae is not known,

but it seems logical to assume that they, in some

way, function in clinging to the substrate. The

vulva, which is always present in the adult

female, is the genital opening and functions in

copulation and egg laying. In some instances,

more than one male is able to mate with a single

female at one time.

The anal rings are often of various shapes in

different mealybugs, but they all function in waste

elimination. As previously mentioned, these

wastes, which are in many instances detrimental

to the mealybug, are propelled long distances

from the body by the rapid contraction of the

walls of the anal cavity. It is also possible that the

anal ring serves as an exit for honeydew intended

for ant consumption and that the long setae of the

ring serve as standards to hold the honeydew

secretion before it is consumed by the ant.

The adult female measures 2.65–2.80 mm in

length and 1.75–1.85 mm in width, and the

females are wingless and as they mature, become

more sessile. The female mealybug has a soft,

oval and flattened segmented body, but the division between the thorax and the abdomen is not

distinct.



6.1.9



Adult Male



The fifth-instar male refers to the adult which is

very complex morphologically and only the easily

recognized characteristics are discussed here.

There are two or three known primary types of



92



dermal pores occurring on male pseudococcids.

The first type is normally clustered in a circular

group on the posterior lateral margin of each side

of the ninth abdominal segment. In Phenacoccus

gossypii Townsend and Cockerell, there is, in

addition to the pair of pore clusters on the ninth

abdominal segment, another pair on the eighth

segment. These pore groupings apparently form

the wax of the long caudal filaments. The pores

which make up these clusters are circular with a

five-pointed star-shaped lumen, are called ‘stellate

pores’. Most of the stellate pore clusters also have

long slender setae, which apparently act as central

bases for the wax of the caudal filaments. It is felt

that the long anal lobe setae of the females might

also function in this manner. The male caudal

filaments of Puto arcloslaphyli Ferris and Puto

decorosus McKenzie, herein described as new,

show a seta in the middle of the long waxy filaments. In Phenacoccus gossypii Townsend and

Cockerell and Pseudococcus longispinus (Targioni

Tozzetti), the above characteristic was observed in

the females. Other types of pores have also been

found on the males and are scattered over the body

surface. These are called ‘dermal disc pores’ and

name the number of loculi they contain. These

may vary from three to five in number with four

being normal, and it is further pointed out that

these structures are by no means flat, but rather are

recessed into the derm, with several small protrusions from the central part of the loculi.

Body setae are also characteristic in the male.

Just as the normal lanceolate setae of the female

are present, so also are the ‘thick, finger-like

digitiform setae’ described by Beardsley. The latter are normally the most common of the two

types; they predominate on both the surfaces of

the body, the legs and especially the antennae.

The ‘digitiform’ setae, which are presumably

sensory in function, are very similar to those on

the last two segments of the female mealybugs’

antenna.

One pair of dorsal ostioles is present on the

submarginal portion of the seventh abdominal

segment and corresponds to the posterior pair of

ostioles on the female. The antennae of the adult

male normally have ten segments, but occasionally there are species which have nine-segmented



M. Mani and C. Shivaraju



antennae, such as Palmicola palmarum (Ehrhorn).

The male has six eyes – a ventral pair, a lateral

pair and a dorsal pair. The eyes of most males are

dark red, with the smaller lateral pair protruding

more than the other two. The mouthparts of the

male are almost nonexistent and are completely

non-functional. All that remains of the mouth is a

small circular opening found at the posterior margin of the ventral part of the head. Normally,

there is one pair of wings which develope from

the mesothorax; these wings possess two longitudinal veins, the anterior one being the radius and

the posterior one being the media. There is also a

complex of minute basal veins called the ‘costal

complex of wing veins’. There are three forms of

males, the first form has fully developed wings

(macropterous); the second form has wings, but

they are reduced and nonfunctional (brachypterous); and the third form is wingless (apterous).

Examples of the first form are Phenacoccus gossypii Townsend and Cockerell, Planococcus cilri

(Risso), Puto lalicribellum Mc- Kenzie

Saccharicoccus sacchari (Cockerell); of the second form is Palmicola palmarum (Ehrhorn); and

of the third form are Puto ambiguus (Fullaway),

P. echinalus McKenzie and P. pacificus

McKenzie. A pair of halteres is present on the

metathorax; they are slender projections adorned

with one or more setae at their tips. The normal

number of apical setae is one, but four have been

on each haltere in Puto yuccae (Coquillett). The

apical setae, whether four or more in number, are

re-curved in such a manner so as to hook into a

circular pocket in the posterior part of the

forewing.

There are two pairs of spiracles in the male,

just as in the female, but in the case of the male

there is often a much more strongly developed

peritreme. The legs of most males are quite similar to those of the females, although they are usually proportionately much longer and more

slender. The tarsus of the male has two segments

rather than the normal single segment of the

female, although in most cases the additional

segment is quite small and appears as a slightly

sclerotized ring. The digitules of the tarsal claws

of most males differ from the spatulate type of

the female in being slender and setiform. The



6 Biology



claw is normally without a denticle. The external

genitalia in male is relatively simple, consisting

of a large penile sheath, a conspicuous vertical

slit and the penis or aedeagus. The penile sheath

is normally large and sclerotized with a posterior

apical projection; this projection maybe of various shapes, but is usually broadly oval. On the

ventral surface of the sheath, there is a noticeable

slit from which the aedeagus often protrudes, is

normally tube-shaped and curves downward. The

penile sheath is apically of various shapes, from

broad as in Pseudococcus fragilis Brain, to very

sharp and pointed as in P. longispinus (TargioniTozzetti). The male of Puto yuccae (Coquillett),

as well as many others of the Puto group, is quite

different from the ‘normal’ Pseudococcid male.

The primary differences noted were eight pairs of

eyes, four setae on each halter, a toothed and

bifurcate aedeagus and a denticle on the claw.

The adult male has a brown-coloured body,

bears two white, anal filaments and is about

1.5 mm in length. The development of the egg to

an adult male or female mealybug takes about

24–26 days, but this can vary for different species

under different climatic factors in different host

plants. The population of the male mealybug is

generally very low, compared to the females; the

male to female ratio varies from 1:5 to 1:8, but

again, this is highly variable for different

species.

The biology of the mealybug varies with different temperature conditions. The number of

generations is quite variable in the

Pseudococcidae; there are eight life cycles in

approximately 1 year. In most of the Puto species, however, only one generation occurs annually and in Puto sandini Washburn, a high-altitude

species, there is one generation every 4 years.



6.2



Biology of Important

Mealybug Species



6.2.1



Antonina graminis



93



the young ones are produced over a period of up

to 2 months. On average, there are 170 offspring

per female during the spring and about 150 in the

summer. The first-instar nymphs are motile, but

the succeeding instars are sessile and produce the

felted wax covering from which a characteristic

excretory tube protrudes. A generation may take

4–6 weeks, depending upon temperature and

location.



6.2.2



Reproduction of B. rehi Lindinger is mainly by

thelyotokous parthenogenesis, viviparous parthenogenesis and, to some extent, by oviparous sexual reproduction. The oviposition period has

been reported to be 2–4 days and the total number of eggs laid by a female varies from 42 to

144, although up to 350 eggs has also been

recorded. The eggs are hyaline to yellowishwhite or pinkish-white and are elongate oval in

shape. They are laid in groups in between the leaf

sheath under the ‘mealy’ covering; the incubation

period ranges from a few minutes to 39 h, with

the hatchability of the eggs varying from 41.7 to

93.5 %. The newly hatched nymphs are crowded

within the waxy threads for 6–10 h before they

disperse to various parts of the same plant. The

pale yellowish nymph is active and the body gets

covered with the waxy material on the second

day. The nymphal period varies from 3 to 4

weeks, where the mature females lay eggs for

about the same duration. The male nymphs gradually develop wings after the first few moults and

emerge as small, active, flying insects; they are

rarely seen and generally mate with females

before dying a day or two after their emergence.

Adult females are wingless, robust, pink and

oval.



6.2.3



The mealybug A. graminis (Maskell) reproduces

unisexually and up to five generations are produced each year. Eggs hatch within the body and



Brevennia rehi



Cataenococcus ensete



Ensete root mealybug C. ensete Williams and

Matile-Ferrero is a serious pest in southern

Ethiopia. The females are viviparous and produce 253 nymphs/females. The average duration



M. Mani and C. Shivaraju



94



of the first-, second- and third-instar nymphs was

16.2, 18.1 and 19.7 days, respectively. The average lifespan of the adult female is 49.9 days. The

body length and width of the adult female mealybugs ranged between 2.9–4 mm and 2.5–3.5 mm,

respectively, when measured inclusive of the wax

covering. Adult female mealybugs could not survive more than 3 weeks in the soil in the absence

of plant materials.



6.2.4



Coccidohystrix insolita



The adult female has very little dorsal wax and

secretes a white, waxy ovisac up to 6 times as long

as its own body, which is more typical of some

Coccidae. The immature stages do not secrete a

thick layer of mealy wax, the body being shiny

yellow-green with submedian grey spots on two

abdominal segments and one thoracic segment.

The female and male nymphs of C. insolita,

reared in mass on sprouted potato tubers, at 22

and 33 °Cand 60–96 % RH, completed ecdysis at

the age of 13.92 and 14.60 days, respectively.

The ratio of female:male was 3.24:1. Starvation

of impregnated females had no adverse effect on

their oviposition. The increase in age of impregnation from 5 to 40 days in females had little

effect on the preoviposition and oviposition periods and the incubation period of eggs. Fecundity

is about 261 days and the longevity varies from

17.66 to 51.6 days. Thirty- to forty-day-old

females showed 77–88 % and 96–99 % reduction

in oviposition period and fecundity, respectively.



6.2.5



Dysmicoccus spp.



There are two separate species of Dysmicoccus

found on pineapple plants. The pink mealybug

Dysmicoccus brevipes (Cockerell) which reproduced non-sexually and the gray mealybug

Dysmicoccus neobrevipes Beardsley which was

bisexual. D. brevipes reproduces non-sexually

through a process called parthenogenesis in

which females birth female larvae without fertilization by males in Hawaii. In areas such as

Brazil, where males are present, both sexual and



non-sexual reproduction occurs. In summer,

both the species produce living young over a

3–4-week period, with the Dysmicoccus neobrevipes produces 346 offspring per individual and

D. brevipes produces 246. The first, second and

third instars or larval stages last for 10–26 days,

6–22 days and 7–24 days, respectively. Thus, the

total nymphal period varies from 26 to 55 days,

with the average being about 34 days. The pink

form starts reproducing parthenogenetically

about 25 days after the third moult, whereas the

gray form produces males in about a 1:1 ratio

and mating is necessary for reproduction.

Unmated females may live for nearly 4 months

awaiting fertilization. There are multiple overlapping generations, with the life cycle of some

being at least twice as long as that of others,

reared under similar conditions. Adult females

are plump and have a convex body, and are pinkish in colour. Lateral wax filaments are usually

less than one fourth as long as the breadth of the

body and those towards the back of the insect are

half as long as the body. The fecundity of the

female was 658.58 nymphs/ovisac and the prelarviposition period for adult females lasts for

about 27 days. The larviposition (giving birth to

larvae) period lasts for an average of 25 days,

they give birth to about 234 progeny, but may

produce up to 1000 crawlers. It may then live for

another 5 days before dying. The duration of the

adult female life varies from 31 to 80 days, averaging about 56 days. Male pineapple mealybugs

do not exist in Hawaii; they are observed from

Brazil. Male pineapple mealybug males are distinguished from the gray pineapple mealybug

males by the difference in the number of antennal segments. The pineapple mealybug has eight

antennal segments and the gray pineappple

mealybug has ten. In addition, the pineapple

mealybug has short clavate setae on its body and

appendages instead of the digitiform setae that is

found on gray pineapple mealybugs. The duration of the adult female life varies from 31 to 80

days, averaging about 56 days, where, the prelarviposition, larviposition and post-larviposition periods last for an average of 27, 25 and 5

days, respectively. They give birth to about 234

progeny, but may produce up to 1000 crawlers.



Tài liệu bạn tìm kiếm đã sẵn sàng tải về

8 Other Targets for Molecular Identification of Insects

Tải bản đầy đủ ngay(0 tr)

×